Tag: optical tweezers

Schematic illustration of the tractor beam set-up. The particles (red balls) are held between a mirror (lower sheet) and a transparent slide (upper sheet). Laser light (green) is focused at the region between the mirror and slide, causing the particles to arrange themselves neatly at the left. Image courtesy of O Brzobohatý et al.

While the country song by this title refers to tractors in an agricultural context, the tractor beam is actually a theoretical physics concept. This beam is said to draw particles toward its source instead of pushing them away. Since the theoretical existence of such a sci-fi-style beam was first proposed a few years back, most physicists have come to accept the concept, and many have been trying to prove its existence ever since.

Now researchers in the Czech Republic have built the first working example of this technology. Not only did their real-life tractor beam attract polystyrene particles, but the researchers were surprised to find it could also sort them.

Dust, rather than Corellian light freighters, are the objects in question: the hope is to use tractor beam tech to collect atmospheric particles or grab dust from a planet’s surface without resorting to using a drill, as the Mars rovers have. And indeed, one of the three methods—optical tweezers—has been used by biologists for decades to hold microscopic particles, including viruses and bacteria, in place for experiments.

The challenge will be developing techniques that will work in all the different environments that an exploratory craft might explore. Optical tweezers won’t work in the vacuum of space, for example, but could be useful on a planet with an atmosphere. The other techniques, which use solenoid beams and Bessel beams, could work at a variety of distances and perhaps without an atmosphere—the NASA team will spend the next decade or so exploring how they might be developed and incorporated.